Eurasian Watermilfoil

Many of you have noticed a substantial increase in the manifestation of aquatic weeds, including the Milfoil variety, which is an extremely fast-growing type. This weed has been a menace to most lakes in North America and has actively expanded north in the past three decades. It is now a reality that we are confronting on Pemichangan and, although there are very few methods of controlling this problem, we can all take some precautionary measures to slow down its spreading.

The FLP’s Milfoil Action Committee is working hard on your behalf to combat this problem. In addition, during the summer of 2007, Lake Pemichangan hosted a study by researchers from the University of Quebec in Montreal. Click here for a report on that study.

Please take the time to read the information below. For additional, more technical details, see the links at the end of this page or this website (external).

Eurasian Milfoil is an invasive species that was introduced to North America via the southern United States in the 1940′s. Since then, milfoil has spread thanks to a number of agents including boaters, fishermen and waterfowl. Milfoil now covers half of North America and can be found in many places in Lake Pemichangan.

Milfoil can grow up to ten metres in height, but will generally reach anywhere from one to four metres. The plant is rooted to the bottom of lakes and grows toward the surface. When the surface is reached, the plant branches, creating a carpet of vegetation.

Milfoil reproduces primarily by fragmentation (piping). Therefore, a small piece of stem that is broken off of the plant can take root and re-colonize an entire area. Each stem can easily reproduce twenty new plants. This aspect of Milfoil makes motor boats especially dangerous to its propagation since the propellers will chop the plant in several pieces – creating upwards of a hundred new plants in the vicinity.

Why worry about Milfoil?

One study conducted in 1992 found Milfoil to be one of five invasive alien plants that have had a major impact on natural ecosystems in Canada. Some of the reasons are indicated below.

Water quality : A higher concentration of coliforms (e-coli) and other bacteria can be found where milfoil has overtaken an area. The pH levels (acidity) of the lake also increase during the summer months. The weed also has the potential to create public health problems associated with increases in some mosquito populations (West Nile) )

Fauna : Milfoil grows so densely that it tends to displace all other species. Furthermore, the natural chemicals found in the lake are disrupted provoking the disappearance of natural fauna habitat.

Fish : Studies have also shown that milfoil has an impact on fish populations by interfering with spawning. Lake Murray (PQ) had to introduce thousands of Splake trout during the spring of 2003 as a result of Milfoil.

Recreational use : Infestations of the plant may create public safety problems when swimmers become entangled in dense stands of the plant. This means that waterskiing in infested areas is out of the question. Furthermore, Milfoil can create such dense foliage that in some places it would be simply impossible for motor boats to function. Seadoos have to refrain from going into a bed of these plants as they will fill up and block the propulsion components of the motor. Moreover, any propeller action will provoke a multiplication of plants which will contribute to additional Milfoil plants in the lake.

Finally, due to the negativity attached to milfoil, the value of your cottage or residence may decline considerably.

Can Milfoil be eliminated or controlled?

Many methods have been tried in the United States and Canada to contain or eliminate milfoil. Due to the rapid spread of the weed over the past decades, it is obvious that these methods have had limited, if any, success.

Mechanical harvesters can quickly reduce the amount of milfoil, however in the long term this method is ineffective since the pipings (cuttings) can enhance the spread of the plant. Diver-operated dredges operate like underwater vacuum cleaners and remove all plant life from the bottom. However this is a very slow and expensive process and is therefore only recommended for limited infestations.

Although it’s mechanisms are not fully understood water circulation has shown some promising results in dramatically reducing Milfoil. A floating pump powered by wind or electricity can clear as area up to 100 metres in diameter. More information can be found at
Currently, biologists are experimenting with a type of weevil to control the spread of Milfoil. The aquatic insect eats the leaves of the Milfoil thus reducing its propagation and even eliminating it. Your association will follow these closely.

What steps should cottagers take?

Uprooting the plant would seem like a good idea, but beware, if each plant isn’t completely uprooted, its pipings will cause the weed to propagate. However it is possible to clear small surfaces of the plant if you ensure that the roots are pulled from the lake bottom and that any stray pieces are thrown far onto the shore. Due to the nature of the plant however, one will be required to repeat the task of uprooting again and again.

While it presently seems that milfoil can’t be eliminated, we can do our best to control it. This can be done in the following ways;

1. Mark an infested area with a buoy.
2. Don’t drive your motor boat through an infested area – even the smallest piece of piping can cause the milfoil to spread throughout the entire lake.
3. Clean your boat, motor or trailer of all particles after visiting another body of water. Empty the hold or livewell of your boat on land and not in the lake. The cooperation of boat launch operators to provide information and washing assistance will be sought in 2004. Milfoil boat-washing precautions also will be useful in preventing the spread of zebra mussels, the incidence of which is being reported in our Region.
4. Stop using detergents and soaps containing phosphates and NEVER use fertilizers or pesticides on your lawn or garden. Lawns are the number one cause of lake deterioration.
5. Ensure that your lot and shoreline are forested.
6. Ensure that your septic system conforms to municipal regulations.

Quite simply, pollution from detergents, phosphates, fertilizers as well as the degradation of the shoreline all produce identical effects: they all provide the lake with excess nutrients causing Milfoil and other weeds to propagate unnaturally fast. Thus, ever larger areas of the Lake will be choked by excess vegetation.

If we all make efforts to follow the suggested measures, we can slow down the spread of milfoil and increase the quality of the lake. Thank you for your cooperation.

The FLP wishes to thank the Lac Quinn, Lac Cayamant and Murray Lake Associations for their assistance.